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Pediplain
In geology and geomorphology a pediplain (from the Latin ''pes'', genitive case ''pedis'', meaning "foot") is an extensive plain formed by the coalescence of pediment (geology), pediments. The processes through which pediplains forms is known as pediplanation. The concepts of pediplain and pediplanation were first developed by geologist Lester Charles King in his 1942 book ''South African Scenery''. The concept gained notoriety as it was juxtaposed to peneplain, peneplanation. The coalesced pediments of the pediplains may form a series of very gentle concave slopes. Pediplains main difference to William Morris Davis, W. M. Davis’ peneplains is in the history and processes behind, and less so in the final shape. Perhaps the most notable difference in form that may be present is that of residual hills which in Davis’ peneplains are to have gentle slopes while in pediplains they ought to have the same steepness as the slopes in the early stages of erosion leading to pediplanati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peneplain
In geomorphology and geology, a peneplain is a low-relief plain formed by protracted erosion. This is the definition in the broadest of terms, albeit with frequency the usage of peneplain is meant to imply the representation of a near-final (or penultimate) stage of fluvial erosion during times of extended tectonic stability. Peneplains are sometimes associated with the cycle of erosion theory of William Morris Davis, but Davis and other researchers have also used the term in a purely descriptive manner without any theory or particular genesis attached. Discussion 390px, Sketch of a hypothetical peneplain formation after an orogeny. The existence of some peneplains, and peneplanation as a process in nature, is not without controversy, due to a lack of contemporary examples and uncertainty in identifying relic examples. By some definitions, peneplains grade down to a base level represented by sea level, yet in other definitions such a condition is ignored. Geomorphologist K ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pediment (geology)
A pediment, also known as a concave slope or waning slope, is a very gently sloping (0.5°–7°) inclined bedrock surface. It is typically a concave surface sloping down from the base of a steeper retreating desert cliff, escarpment, or surrounding a monadnock or inselberg, but may persist after the higher terrain has eroded away. Pediments are erosional surfaces. A pediment develops when sheets of running water ( sheet floods) wash over it in intense rainfall events. It may be thinly covered with fluvial gravel that has washed over it from the foot of mountains produced by cliff retreat erosion. A pediment is not to be confused with a bajada, which is a merged group of alluvial fans. Bajadas also slope gently from an escarpment, but are composed of material eroded from canyons in the escarpment and redeposited on the bajada, rather than of bedrock with a thin veneer of gravel. Description Pediments were originally recognized as the upper part of smoothly sloping (0.5°- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planation Surfaces
In geology and geomorphology a planation surface is a large-scale land surface that is almost flat with the possible exception of some residual hills. The processes that form planation surfaces are labelled collectively planation and are exogenic (chiefly erosion). Planation surfaces are planated regardless of bedrock structures. On Earth, they constitute some of the most common landscapes. Geological maps indicate that planation surfaces may comprise 65% of the landscapes on Saturn's largest moon, Titan, which hosts a hydrological cycle of liquid methane. Peneplains and pediplains are types of planation surfaces planated respectively by "peneplanation" and "pediplanation". In addition to these there are planation surfaces proposed to be formed by cryoplanation, marine processes, areal glacial erosion and salt weathering. The term ''planation surface'' is often preferred over others because some more specific planation surface types and processes remain controversial. Etchplains ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lester Charles King
Lester Charles King (1907–1989) was an English geologist and geomorphologist known for his theories on scarp retreat. He offered a very different view of the origin of continental landscaping than that of William Morris Davis. Studying at university in New Zealand King was a disciple of Charles Cotton who was heavily influenced by Davis. While King's ideas were an attempt at refuting Davis' cycle of erosion they were themselves of cyclical nature and contributed to what Cliff Ollier has called "Davis bashing" — the ridicule of cyclical theories in geomorphology, in particular Davis' ones. Critics did however not propose alternative models. For him, the weathering of physical factors in arid areas causes the erosion of the hills, the deposition of the weathered material (pediments) and the deposition of these material in lower altitudes, contributing to the formation of the pediplain. He was also an early proponent of continental drift Continental drift is a highly s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hillslope Evolution
Hillslope evolution is the changes in the erosion rates, erosion styles and form of slopes of hills and mountains over time. Conceptual models During most of the 20th century three models of hillslope evolution were widely diffused: slope decline, slope replacement and parallel slope retreat. Until the 1950s models of hillslope form evolution were central in geomorphology. The modern understanding is that the evolution of slopes is much more complex than the classical models of decline, replacement and retreat imply. Slope decline Slope decline was proposed by William Morris Davis in his cycle of erosion theory. It consists of a gradual decrease in slope angle as stream incision slows down. This is accompaigned as slopes becomes more gentle they accumulate with fine-grained regolith stemming from weathering. Slope replacement Slope replacement was first proposed by Walther Penck challenging Davis' ideas on slope development. Slope replacement describes an evolution of slope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryoplanation
In geomorphology, cryoplanation or is a term used to both describe and explain the formation of plains, terraces and pediments in periglacial environments. Uncertainty surrounds the term, and the effectiveness of the cryoplanation process is held to be limited meaning it can only produce small terraces. Instead, many of so-called cryoplanation terraces are likely an expression of the underlying lithology and rock structure rather than being unique products of cold-climate processes. Cryoplanation can be seen as a variant of pediplanation that is restricted to cold climates. All the cryoplanation surfaces that exist at present date to the Quaternary. History of the concept The existence of flat bedrock surfaces in the mountains of Siberia was noted in the 1930s. Soviet scientists S.G. Boch and I.I. Krasnov first proposed a cyclical model for the formation these surfaces in 1943. This model influenced central and western European geomorphologists. Carl Troll, writing in German, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Etchplanation
An etchplain is a plain where the bedrock has been subject to considerable "etching" or subsurface weathering. Etchplanation is the process forming etchplains. Contrary to what the name might suggest, etchplains are seldom completely flat and usually display some relief, as weathering of the bedrock does not advance uniformly. This means that weathering is unrelated to the flatness which might be derivative of various other processes of planation including peneplanation and pediplanation. Erosion of etchplains can result in the exposure of inselbergs such as bornhardt and tors. Generally the topography exposed at a stripped etchplain, that is an etch surface, after erosion of regolith is one with many irregularities as result of structurally defined areas of rock strength. A distinction can be made between etchplains and etch surfaces as the latter may or may not be flat and can represent the landform arising from the stripping of an etchplain. As climate changes, arid and s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semi-arid
A semi-arid climate, semi-desert climate, or steppe climate is a aridity, dry climate sub-type. It is located on regions that receive precipitation below Evapotranspiration#Potential evapotranspiration, potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on variables such as temperature, and they give rise to different biomes. Defining attributes of semi-arid climates A more precise definition is given by the Köppen climate classification, which treats steppe climates (''BSh'' and ''BSk'') as intermediates between desert climates (BW) and humid climates (A, C, D) in ecological characteristics and agricultural potential. Semi-arid climates tend to support short, thorny or scrubby vegetation and are usually dominated by either grasses or shrubs as they usually cannot support forests. To determine if a location has a semi-arid climate, the precipitation threshold must first be determined. The method used to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeitschrift Für Geomorphologie
The ''Zeitschrift für Geomorphologie'' is a peer-reviewed scientific journal about geomorphology. The journal is indexed in Science Citation Index, GeoRef, Geodok and Scopus Scopus is a scientific abstract and citation database, launched by the academic publisher Elsevier as a competitor to older Web of Science in 2004. The ensuing competition between the two databases has been characterized as "intense" and is c .... It is published by E. Schweizerbart. External links * Earth and atmospheric sciences journals Multilingual journals Geomorphology journals E. Schweizerbart academic journals {{Geomorphology-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Sudan
South Sudan (), officially the Republic of South Sudan, is a landlocked country in East Africa. It is bordered on the north by Sudan; on the east by Ethiopia; on the south by the Democratic Republic of the Congo, Uganda and Kenya; and on the west by the Central African Republic. South Sudan's diverse landscape includes vast plains and plateaus, dry and tropical savannahs, inland floodplains, and forested mountains. The Nile, Nile River system is the defining physical feature of the country, running south to north across its center, which is dominated by a large swamp known as the Sudd. South Sudan has a population of just over 12.7 million in 2024. Juba is the Capital city, capital and largest city. Sudan was occupied by History of Egypt under the Muhammad Ali dynasty, Egypt under the Muhammad Ali dynasty and governed as an Anglo-Egyptian Sudan, Anglo-Egyptian condominium until Sudanese independence in 1956. Following the First Sudanese Civil War, the Southern Sudan Autonomous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atacama Pediplain
The Atacama Desert () is a desert plateau located on the Pacific Ocean, Pacific coast of South America, in the north of Chile. Stretching over a strip of land west of the Andes Mountains, it covers an area of , which increases to if the barren lower slopes of the Andes are included. The Atacama Desert is the driest nonpolar desert in the world, and the second driest overall, behind some specific spots within the McMurdo Dry Valleys. It is the only Desert climate, true desert to receive less precipitation than polar deserts, and the largest fog desert in the world. The area has been used as an experimentation site for Mars expedition simulations due to its similarities to the Martian environment. The constant Inversion (meteorology), temperature inversion caused by the cool north-flowing Humboldt Current, Humboldt ocean current and the strong South Pacific High, Pacific anticyclone contribute to the extreme aridity of the desert. The most arid region of the Atacama Desert is s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Journal Of Geology
''The Journal of Geology'' publishes research on geology, geophysics, geochemistry, sedimentology, geomorphology, petrology, plate tectonics, volcanology, structural geology, mineralogy, and planetary sciences. Its content ranges from planetary evolution to computer modeling of fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ... development, making it relevant to geologists as well as other researchers working in the Earth or planetary sciences. It was established in 1893 by Thomas Chrowder Chamberlin. References External links * English-language journals Bimonthly journals University of Chicago Press academic journals Academic journals established in 1893 Geology journals {{geology-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
